/*
 * Copyright (c) 1998 Michael Smith.
 * Copyright (c) 2000 Maxim Sobolev
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>

#ifndef REGRESSION
#include "stand.h"
#else
#include <stdlib.h>
#include <sys/errno.h>
#include <sys/fcntl.h>
#include <sys/types.h>
#include <sys/unistd.h>

struct open_file {
	int	f_flags;	/* see F_* below */
	void	*f_fsdata;	/* file system specific data */
};
#define	F_READ		0x0001	/* file opened for reading */
#define	EOFFSET	(ELAST + 8)	/* relative seek not supported */
#define	panic(x, y) abort()

static inline uint_t
min(uint_t a, uint_t b)
{
	return (a < b ? a : b);
}
#endif

#include <sys/stat.h>
#include <string.h>
#include <bzlib.h>

#define	BZ_BUFSIZE 2048	/* XXX larger? */

struct bz_file
{
	int		bzf_rawfd;
	bz_stream	bzf_bzstream;
	char		bzf_buf[BZ_BUFSIZE];
	int		bzf_endseen;
};

static int	bzf_fill(struct bz_file *);
static int	bzf_open(const char *, struct open_file *);
static int	bzf_close(struct open_file *);
static int	bzf_read(struct open_file *, void *, size_t, size_t *);
static off_t	bzf_seek(struct open_file *, off_t, int);
static int	bzf_stat(struct open_file *, struct stat *);

#ifndef REGRESSION
struct fs_ops bzipfs_fsops = {
	.fs_name = "bzip",
	.fo_open = bzf_open,
	.fo_close = bzf_close,
	.fo_read = bzf_read,
	.fo_write = null_write,
	.fo_seek = bzf_seek,
	.fo_stat = bzf_stat,
	.fo_readdir = null_readdir
};
#endif

static int
bzf_fill(struct bz_file *bzf)
{
	int		result;
	int		req;

	req = BZ_BUFSIZE - bzf->bzf_bzstream.avail_in;
	result = 0;

	/* If we need more */
	if (req > 0) {
		/* move old data to bottom of buffer */
		if (req < BZ_BUFSIZE) {
			bcopy(bzf->bzf_buf + req, bzf->bzf_buf,
			    BZ_BUFSIZE - req);
		}

		/* read to fill buffer and update availibility data */
		result = read(bzf->bzf_rawfd,
		    bzf->bzf_buf + bzf->bzf_bzstream.avail_in, req);
		bzf->bzf_bzstream.next_in = bzf->bzf_buf;
		if (result >= 0)
			bzf->bzf_bzstream.avail_in += result;
	}
	return (result);
}

/*
 * Adapted from get_byte/check_header in libz
 *
 * Returns 0 if the header is OK, nonzero if not.
 */
static int
get_byte(struct bz_file *bzf)
{
	if ((bzf->bzf_bzstream.avail_in == 0) && (bzf_fill(bzf) == -1))
		return (-1);
	bzf->bzf_bzstream.avail_in--;
	return (*(bzf->bzf_bzstream.next_in)++);
}

static int bz_magic[3] = {'B', 'Z', 'h'}; /* bzip2 magic header */

static int
check_header(struct bz_file *bzf)
{
	unsigned int len;
	int		 c;

	/* Check the bzip2 magic header */
	for (len = 0; len < 3; len++) {
		c = get_byte(bzf);
		if (c != bz_magic[len]) {
			return (1);
		}
	}
	/* Check that the block size is valid */
	c = get_byte(bzf);
	if (c < '1' || c > '9')
		return (1);

	/* Put back bytes that we've took from the input stream */
	bzf->bzf_bzstream.next_in -= 4;
	bzf->bzf_bzstream.avail_in += 4;

	return (0);
}

static int
bzf_open(const char *fname, struct open_file *f)
{
	static char		*bzfname;
	int			rawfd;
	struct bz_file	*bzf;
	char		*cp;
	int			error;
	struct stat		sb;

	/* Have to be in "just read it" mode */
	if (f->f_flags != F_READ)
		return (EPERM);

	/* If the name already ends in .gz or .bz2, ignore it */
	if ((cp = strrchr(fname, '.')) &&
	    ((strcmp(cp, ".gz") == 0) ||
	    (strcmp(cp, ".bz2") == 0) ||
	    (strcmp(cp, ".split") == 0)))
		return (ENOENT);

	/* Construct new name */
	bzfname = malloc(strlen(fname) + 5);
	if (bzfname == NULL)
		return (ENOMEM);
	sprintf(bzfname, "%s.bz2", fname);

	/* Try to open the compressed datafile */
	rawfd = open(bzfname, O_RDONLY);
	free(bzfname);
	if (rawfd == -1)
		return (ENOENT);

	if (fstat(rawfd, &sb) < 0) {
		printf("bzf_open: stat failed\n");
		close(rawfd);
		return (ENOENT);
	}
	if (!S_ISREG(sb.st_mode)) {
		printf("bzf_open: not a file\n");
		close(rawfd);
		return (EISDIR);		/* best guess */
	}

	/* Allocate a bz_file structure, populate it */
	bzf = malloc(sizeof (struct bz_file));
	if (bzf == NULL)
		return (ENOMEM);
	bzero(bzf, sizeof (struct bz_file));
	bzf->bzf_rawfd = rawfd;

	/* Verify that the file is bzipped */
	if (check_header(bzf)) {
		close(bzf->bzf_rawfd);
		free(bzf);
		return (EFTYPE);
	}

	/* Initialise the inflation engine */
	error = BZ2_bzDecompressInit(&(bzf->bzf_bzstream), 0, 1);
	if (error != BZ_OK) {
		printf("bzf_open: BZ2_bzDecompressInit returned %d\n", error);
		close(bzf->bzf_rawfd);
		free(bzf);
		return (EIO);
	}

	/* Looks OK, we'll take it */
	f->f_fsdata = bzf;
	return (0);
}

static int
bzf_close(struct open_file *f)
{
	struct bz_file	*bzf = (struct bz_file *)f->f_fsdata;

	BZ2_bzDecompressEnd(&(bzf->bzf_bzstream));
	close(bzf->bzf_rawfd);
	free(bzf);
	return (0);
}

static int
bzf_read(struct open_file *f, void *buf, size_t size, size_t *resid)
{
	struct bz_file	*bzf = (struct bz_file *)f->f_fsdata;
	int			error;

	bzf->bzf_bzstream.next_out = buf;	/* where and how much */
	bzf->bzf_bzstream.avail_out = size;

	while (bzf->bzf_bzstream.avail_out && bzf->bzf_endseen == 0) {
		if ((bzf->bzf_bzstream.avail_in == 0) &&
		    (bzf_fill(bzf) == -1)) {
			printf("bzf_read: fill error\n");
			return (EIO);
		}
		if (bzf->bzf_bzstream.avail_in == 0) {
			/* oops, unexpected EOF */
			printf("bzf_read: unexpected EOF\n");
			if (bzf->bzf_bzstream.avail_out == size)
				return (EIO);
			break;
		}

		/* decompression pass */
		error = BZ2_bzDecompress(&bzf->bzf_bzstream);
		if (error == BZ_STREAM_END) {		/* EOF, all done */
			bzf->bzf_endseen = 1;
			break;
		}
		if (error != BZ_OK) {	/* argh, decompression error */
			printf("bzf_read: BZ2_bzDecompress returned %d\n",
			    error);
			return (EIO);
		}
	}
	if (resid != NULL)
		*resid = bzf->bzf_bzstream.avail_out;
	return (0);
}

static int
bzf_rewind(struct open_file *f)
{
	struct bz_file	*bzf = (struct bz_file *)f->f_fsdata;
	struct bz_file	*bzf_tmp;

	/*
	 * Since bzip2 does not have an equivalent inflateReset function a crude
	 * one needs to be provided. The functions all called in such a way that
	 * at any time an error occurs a roll back can be done (effectively
	 * making this rewind 'atomic', either the reset occurs successfully
	 * or not at all, with no 'undefined' state happening).
	 */

	/* Allocate a bz_file structure, populate it */
	bzf_tmp = malloc(sizeof (struct bz_file));
	if (bzf_tmp == NULL)
		return (-1);
	bzero(bzf_tmp, sizeof (struct bz_file));
	bzf_tmp->bzf_rawfd = bzf->bzf_rawfd;

	/* Initialise the inflation engine */
	if (BZ2_bzDecompressInit(&(bzf_tmp->bzf_bzstream), 0, 1) != BZ_OK) {
		free(bzf_tmp);
		return (-1);
	}

	/* Seek back to the beginning of the file */
	if (lseek(bzf->bzf_rawfd, 0, SEEK_SET) == -1) {
		BZ2_bzDecompressEnd(&(bzf_tmp->bzf_bzstream));
		free(bzf_tmp);
		return (-1);
	}

	/* Free old bz_file data */
	BZ2_bzDecompressEnd(&(bzf->bzf_bzstream));
	free(bzf);

	/* Use the new bz_file data */
	f->f_fsdata = bzf_tmp;

	return (0);
}

static off_t
bzf_seek(struct open_file *f, off_t offset, int where)
{
	struct bz_file	*bzf = (struct bz_file *)f->f_fsdata;
	off_t		target;
	char		discard[16];

	switch (where) {
	case SEEK_SET:
		target = offset;
		break;
	case SEEK_CUR:
		target = offset + bzf->bzf_bzstream.total_out_lo32;
		break;
	default:
		errno = EINVAL;
		return (-1);
	}

	/* Can we get there from here? */
	if (target < bzf->bzf_bzstream.total_out_lo32 && bzf_rewind(f) != 0) {
		errno = EOFFSET;
		return (-1);
	}

	/* if bzf_rewind was called then bzf has changed */
	bzf = (struct bz_file *)f->f_fsdata;

	/* skip forwards if required */
	while (target > bzf->bzf_bzstream.total_out_lo32) {
		errno = bzf_read(f, discard, min(sizeof (discard),
		    target - bzf->bzf_bzstream.total_out_lo32), NULL);
		if (errno)
			return (-1);
	}
	/* This is where we are (be honest if we overshot) */
	return (bzf->bzf_bzstream.total_out_lo32);
}

static int
bzf_stat(struct open_file *f, struct stat *sb)
{
	struct bz_file	*bzf = (struct bz_file *)f->f_fsdata;
	int		result;

	/* stat as normal, but indicate that size is unknown */
	if ((result = fstat(bzf->bzf_rawfd, sb)) == 0)
		sb->st_size = -1;
	return (result);
}

void
bz_internal_error(int errorcode)
{
	panic("bzipfs: critical error %d in bzip2 library occured",
	    errorcode);
}

#ifdef REGRESSION
/* Small test case, open and decompress test.bz2 */
int
main()
{
	struct open_file f;
	char buf[1024];
	size_t resid;
	int err;

	memset(&f, '\0', sizeof (f));
	f.f_flags = F_READ;
	err = bzf_open("test", &f);
	if (err != 0)
		exit(1);
	do {
		err = bzf_read(&f, buf, sizeof (buf), &resid);
	} while (err == 0 && resid != sizeof (buf));

	if (err != 0)
		exit(2);
	exit(0);
}
#endif
